Process of manufacturing chlorinated hydrocarbons



Sept. 9, 1952 1 VANHAREN 2,610,215

l PROCESS 0F MANUFACTURING CHLORINATED HYnRocARBoNs Filed April 11, 195oPatented Sept. 9, 1952 PROCESS Lambertvvanharen,IxelleshBruss'els,Belgium; as-

signor to Solvay & Cie,V Brussels, Belgium; a

'Belgian .company ApplicationAprilll, 1950, Serial No. 155,265

IniBelgum'AprilZG, 1949 3 Claims. (Cl. 26m-654i 1 2 l The invention`relates to a cyclic' process 0f monochloroethylene and`1.1dichloroethylene i simultaneously manufacturingl at leasttwochlorinated ethylene. hydrocarbons.

Amongst the various known processes, the most current process for thepreparation of: a chloroethylene hydrocarbon consists in preparing theimmediately highly saturated chlorinated hydrocarbon and in freeing itfrom hydrochloride` by the actionoi an lalkali oryof heats Thus,trichloroethylene is prepared by first carrying out the 4synthesis oftetrachloroethane from acetylene andn chlorine', and then splitting upthe tetrachloroethane into trichloroethylene and hydrogen chloride.

Similarly, monochloroethylene is obtained by preparing1.2-di`chloroethane from ethylene and chlorine', the dicliloroeth'anethen being split up into monochloroethylene and hydrogen chloride.

When itis desired to prepareV a plurality oi.' non-saturated ethylenecompounds; for example `tricl'iloroethylene and percliloroethyl'ene,` it-is therefore first necessaryV to prepare the immediately/highersaturated chlorinatedv hydrocarbons. In the example selected, these aretetrachloroethane and pentachloroethane.

y It has, recently been' `proposed to preparevhydrogen chloride releasedby substituti've chlo rination carriesV off. withv it considerable`amounts ofthe` hydrocarbon, which consequently does'not react withthechlorinein` liquid phase but, in` the case of acetylene for example',gives" rise ingaseous phase to an explosive reaction with theVchlorine.. y

The .process mosti `generally utilized hitherto Y consisted ineiectingsuccessive chlorinationsand dehydrochlorinations, in separateapparatus; in order to obtain they desired hydrocarbons.

Returning to the example of the preparation otftrizfandperchloroethylena. the#v successiveA reactionsare the following:

' rey-Y simnar `re`aeuons`-J is is possible te prepare h carbon andchlorine.

from ethylene and chlorine, by passing' through 1.2-diand1.1.2-trichloroeth'ane'.

The additive chlorination of the' originating hydrocarbons' is generallyeffected in liquid. phase in a mutual solvent of the hydrocarbon and ofchlorine, this solvent being most frequently constituted* bychloroethaneitself.

The speeds of these chlorination reactions are limited by the speeds ofdissolution of'th'e hydro- When 'using chloroethane as' a solvent andreaction medium, the solubility of chlorine is' very great and theprocess is solely limited bythe speed' of dissolution ofthe hydrocarbon.The capacity of the chlorination apparatus is thus limited by the speedof dissolution ofthe latter. If'the hydrocarbon is introduced` into thechlorinator'ata speed higher, than its speed of dissolution', apartpasse's through the liquid bath without dissolvingor reacting; andescapes with the residuarygases. In vthe particular case of reaction(l), this `presents very great inconvenience in View ofthe fact that, asstated hereinabove, acetylene and chlorine react explosively inthegaseousphase.

One of the objects of the' present invention is to provide a process'permitting the increasing' of the capacity of chlorination of theseapparatus, whilekeeping at least constant thecapacities of production ofchloroethane based on the additive reactionsofchlorinevvith theunsaturated hydrocarbons;

Another' object' resides in a cyclic processfor the simultaneousproduction of at least two ethylene hydrocarbons by synthesis ofchloroethanes and dehydrochlorination of the latter.

Itl is based on the surprising" fact that it is possible to obtain theseresults by simultaneously effecting; in the-liquid phase, the additivechlorinations which hitherto have been carried out successively;

For this purpose, according to the invention, thereare introduced into achlorinator; on the one hand, anL unsaturated hydrocarbon and'. theamount' of chlorinecorrespondi'ng to the'addltive chlorination of saidhydrocarbon and, on the other hand, at least onechlorinated ethylenehydrocarbon and" the l amount ofi chlorine corresponding" {QU-theadditlvechlolinalibn Of the latter; said chlorinatedethylene-hyd'rocarbtmsv beingobtainedlby dehydrochlorination of` theAcorresponding chloroethanes:

The accompanying diagrammatic' drawing showsby'wa'y of example one*method of carrying? out tire-process in its particular" application tothe simultaneous preparation of triand perchloroethylene from acetyleneand chlorine.

Into a chlorinator I, which contains a mixture of tetraandpentachloroethane and also a catalyst normally used kfor the additivechlorination of hydrocarbons (for example ferric chloride), there areintroduced, on the one hand, acetylene at 7 and chlorine at 8 in themolecular ratio substantially equal to 1:2, and on the other handtrichloroethylene at 9 and chlorine, also at 8, in the molecular ratiosubstantially equal to 1:1.

The trichloroethylene introduced into the chlorinator comes from theseparation of the tri-perchloroethylene mixture obtained by splitting upthe mixture of tetraand pentachloroethane. 4 v

The method of distribution of the reagents in the chlorinator is notcritical; nevertheless, as suggested in British specication No. 604,384,it is ,possible to dissolve separately one or more of the reagents andto eiect the mixing in the chlorination apparatus.

The latter is connected to a cooler 2 fed with steam or water in suchmanner that by circulation of the mixture of the products of the reaction a substantially constantA temperature is maintained at the top andbottom of the chlorinator, thediference between these two temperaturesbeing advantageously as small as possible.

During` the course of the process of chlorination, the flow of acetyleneand thatof chlorine are regulated so as to obtain a slight excess ofchlorine in solution in the chlorination Vfoot constituted by thetetra-pentachloroethane mixture.

The residual gases, practically free from C2H2, are cooled in acondenser v3, in order to recycle the'chloroethanes carried vby them,and are then v washed in an absorber-scrubber l.- before being passedLto the atmosphere.

The mixture of chloroethanes formed is withdrawn at l@ and passedfon todehydrochlorination.. This operation may be eiected by thermal A'dissociation or else by chemical reaction with an alkaline solution. Inthe method of operating illustrated, themixture is introduced at Il onthe bottom platforms of a column 5, while milk of lime is introducedabove the chloroethanes at It. The column is heated by the introductionof live steam at I6. From the top of this column passes out atri-perchloroethylene-water mixture toa condenser I'I, whence a part ofthis mixture flows back to the column whiley the other part isintroduced after drying to the rectifying column Il. Y From the base ofthe column is taken at I3 the aqueous solution of CaClz, as -well as anytraces of hexachloroethane. At the top of; the

, column E is removed the trichloroethylene which Vis co-ndensed at I8,and of which a fraction is taken as nished product at I4, while theother fraction is recycled to the chlorinator through the pipe il.-

At4 the base of the rectification column, at I5, the perchloroethyleneis removed.

Without departing from the scope of the invention, the cycle describedabove can obviously'be mixture, `the dissociation of thechloroethanesbe-Y ing then carried out by thermal or chemical means on.each of the products rectied.

, The invention is not limited solely to the simul- I taneouspreparation of triand perchloroethylene by chlorination of acetylene andrecycled tri- 4 chloroethylene. It is also applicable to the preparationof other ethylene hydrocarbons, particularly monochloroethylene and1.1-dichloroethylene.

ln this case diand trichloroethane are prepared simultaneously bychlorination of ethylene and monochloroethylene which is recycled, thelatter being obtained in per se known manner by thermal or chemicaldissociation of V1.2-dichloroethane. As it has been stated above, theinvention aims at the formation of chloroethane by additive reactions.Nevertheless, it is known that in the synthesis` of tetrachloroethane,for example, small amounts of pentachloroetha-ne are inevitablyproduced. It is not necessary to attempt to avoid this secondaryreaction, because the process of the invention likewise leads to theformation of pentachloroethaner by chlorination of trichloroethyleneobtained by dehydrochlorination, outside the reactor,` from a part ofthe tetrachloroethane produced. It is even possible to producechloroethane substitution Areactions and to combine the process of theinvention with lknown processes of chlorination by substitution;

in this manner it would be possible to vary at will the ratio betweentheamounts of chloroethylene desired, not only by acting 'on the amountof chloroethylene recycled, but also by eiecting the substitution ofthechloroethane obtained by additive chlorination of the unsaturatedhydrocarbon; nevertheless, this would obviously be at the expense of thecapacity of production of the chlorinator.

The reactions of formation of the chloroethanes being highlyexother'rnic7 it is important that the .cooling should be sufficientlyeffective to be able to maintain the temperature in the chlorinatorwithin the limits compatible with the good Theseconditions beingfulfilled, the process'has the advantage of permitting` the carryingout, in a pre-existing apparatus, `of at least one supplementaryaddition reaction without reducing the capacity of absorption ofhydrocarbon of the apparatus.

The process according to the invention therefore offers the advantage ofpermitting the preparation in existing installations of4 atleast twochlorinated ethylene hydrocarbons without reducing the daily Vcapacityof the installations, while requiring as supplementary capital outlayonly the apparatus necessary for the separation of the mixturesprepared.

The process is particularly interesting for the simultaneous preparationof triand perchloroethylene which, by reason of their differentproperties, vapour tension, solvent power, and toxicity, both have,either alone or mixed, various applications as solvents.

The process is likewise interesting for .the simultaneous production ofmonoand 1.1-dichloroethylene, these products, isolated or in mixture,being used as starting material for the preparation of'synthetic plasticmaterials.

Example Into an apparatus normally used for vthe production oftetrachloroethane by additive chlorination of acetylene, and having amaximum capacity of productionfof tetrachloroethane of 3600 kg. per diemfor mean temperatures in the 'chlorinator of 85 C at thebottom and 110C. at the top, there'are introduced, in addition to theamounts ofacetylene and chlorine necessary for the synthesis of the 3600 kg. oftetrachloro- 5 ethane, 800 and 426 kg. per diem respectively oftrichloroethylene and chlorine. When working is underway, the mixture ofchloroethanes produced contains 26% of pentachloroethane.

By dehydrochlorination of these chloroethanes,

a mixture of triand perchloroethylene is obtained, from which 80G kg.per diem or trichloroethylene are separated for recycling and of whichsubstantially v20il0 kg. per diem of triand 1000 kg. per diem 'ofperchloroethylene are taken as iinished product.

@maximum rate compatible with no free acet-v ethane andpentachloroethane in the liquidphase, said acetylene being introduced atthe fylene reaching the top'v of the chlorination No modiication havingbeen made to the system of cooling, the mean temperatures in the reactorhave risen respectively to 92.5 C. at they;

in view of the fact that within these tempera-r ture limits thesolubility of acetylene is lower in chloroethane alone.

This example shows that in an apparatus oi kzone and said chlorinef'gasbeing introduced at `a rate slightly in excess of thatstoichiometricallyrequired for the additive chlorination of both saidacetylene andfsaid trichloroethylene,

thereby forming tetiacliloroethane and pentan Yfrom the chlorinationzone subjecting said mixchloroethane, withdrawing; the reaction mixtureture to dehydrochlorination, whereby to obtain a-mixture oftrichloroethylene and perchloroethylene, separating saidtrichloroethylene from said perchloroethylene, withdrawing a portion ofSaid trichloroethylene and 1returning the remaining portion of saidtrichloroethylene to said I chlorination zone.

given size for producing tetrachloroethane it is l possible to produce asupplementary reaction by. chlorinating trichloroethylene intopentachlorol ethane without reducing the hourly production oftetrachloroethane.

Iclaim:

1. In a cyclic process for the simultaneous production oftrichloroethylene and perchloroethylene, the steps which comprisesimultaneously introducing chlorine gas, acetylene and trichloroethyleneinto a chlorination zone substantially lled with a mixture oftetrachloro- '12. In a cyclic processjas claimed in claim *1,

circulating the reacting 'mixture through a cooling zone to maintain thetop of the chlorinator at a temperature only slightly above the temf iperature at the bottom thereof. tetrapentachloroethane mixtures than intetranEFERENoEs CITED The following references are of record in the tileof this patent:

UNI'I'ED STATES PATENTS Number Name Date Cass Apr. 28, 1942

1. IN A CYCLIC PROCESS FOR THE SIMULTANEOUS PRODUCTION OFTRICHLOROETHYLENE AND PERCHLOROETHYLENE, THE STEPS WHICH COMPRISESIMULTANEOUSLY INTRODUCING CHLORINE GAS, ACETYLENE AND TRICHLOROETHYLENEINTO A CHLORINATION ZONE SUBSTANTIALLY FILLED WITH A MIXTURE OFTETRACHLOROETHANE AND PENTACHLOROETHANE IN THE LIQUID PHASE, SAIDACETYLENE BEING INTRODUCED AT THE MAXIMUM RATE COMPATIBLE WITH NO FREEACETYLENE REACHING THE TOP OF THE CHLORINATION ZONE AND SAID CHLORINEGAS BEING INTRODUCED AT A RATE SLIGHTLY IN EXCESS OF THATSTOICHIOMATRICALLY REQUIRED FOR THE ADDITIVE CHLORINATION OF BOTH SAIDACETYLENE AND SAID TRICHLOROETHYLENE, THEREBY FORMING TETRACHLOROETHANEAND PENTACHLOROETHANE, WITHDRAWING THE REACTION MIXTURE FROM THECHLORINATION ZONE SUBJECTING SAID MIXTURE TO DEHYDROCHLORINATION,WHEREBY TO OBTAIN A MIXTURE OF TRICHLOROETHYLENE AND PERCHLOROETHYLENE,SEPARATING SAID TRICHLOROETHYLENE FROM SAID PERCHLOROETHYLENE,WITHDRAWING A PORTION OF SAID TRICHLOROETHYLENE AND RETURNING THEREMAINING PORTION OF SAID TRICHLOROETHYLENE TO SAID CHLORINATION ZONE.